[mirror_ubuntu-artful-kernel.git] / lib / asn1_decoder.c

/* Decoder for ASN.1 BER/DER/CER encoded bytestream
 *
 * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public Licence
 * as published by the Free Software Foundation; either version
 * 2 of the Licence, or (at your option) any later version.
 */

#include <linux/export.h>
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/asn1_decoder.h>
#include <linux/asn1_ber_bytecode.h>

static const unsigned char asn1_op_lengths[ASN1_OP__NR] = {
	/*					OPC TAG JMP ACT */
	[ASN1_OP_MATCH]				= 1 + 1,
	[ASN1_OP_MATCH_OR_SKIP]			= 1 + 1,
	[ASN1_OP_MATCH_ACT]			= 1 + 1     + 1,
	[ASN1_OP_MATCH_ACT_OR_SKIP]		= 1 + 1     + 1,
	[ASN1_OP_MATCH_JUMP]			= 1 + 1 + 1,
	[ASN1_OP_MATCH_JUMP_OR_SKIP]		= 1 + 1 + 1,
	[ASN1_OP_MATCH_ANY]			= 1,
	[ASN1_OP_MATCH_ANY_ACT]			= 1         + 1,
	[ASN1_OP_COND_MATCH_OR_SKIP]		= 1 + 1,
	[ASN1_OP_COND_MATCH_ACT_OR_SKIP]	= 1 + 1     + 1,
	[ASN1_OP_COND_MATCH_JUMP_OR_SKIP]	= 1 + 1 + 1,
	[ASN1_OP_COND_MATCH_ANY]		= 1,
	[ASN1_OP_COND_MATCH_ANY_ACT]		= 1         + 1,
	[ASN1_OP_COND_FAIL]			= 1,
	[ASN1_OP_COMPLETE]			= 1,
	[ASN1_OP_ACT]				= 1         + 1,
	[ASN1_OP_MAYBE_ACT]			= 1         + 1,
	[ASN1_OP_RETURN]			= 1,
	[ASN1_OP_END_SEQ]			= 1,
	[ASN1_OP_END_SEQ_OF]			= 1     + 1,
	[ASN1_OP_END_SET]			= 1,
	[ASN1_OP_END_SET_OF]			= 1     + 1,
	[ASN1_OP_END_SEQ_ACT]			= 1         + 1,
	[ASN1_OP_END_SEQ_OF_ACT]		= 1     + 1 + 1,
	[ASN1_OP_END_SET_ACT]			= 1         + 1,
	[ASN1_OP_END_SET_OF_ACT]		= 1     + 1 + 1,
};

/*
 * Find the length of an indefinite length object
 * @data: The data buffer
 * @datalen: The end of the innermost containing element in the buffer
 * @_dp: The data parse cursor (updated before returning)
 * @_len: Where to return the size of the element.
 * @_errmsg: Where to return a pointer to an error message on error
 */
static int asn1_find_indefinite_length(const unsigned char *data, size_t datalen,
				       size_t *_dp, size_t *_len,
				       const char **_errmsg)
{
	unsigned char tag, tmp;
	size_t dp = *_dp, len, n;
	int indef_level = 1;

next_tag:
	if (unlikely(datalen - dp < 2)) {
		if (datalen == dp)
			goto missing_eoc;
		goto data_overrun_error;
	}

	/* Extract a tag from the data */
	tag = data[dp++];
	if (tag == 0) {
		/* It appears to be an EOC. */
		if (data[dp++] != 0)
			goto invalid_eoc;
		if (--indef_level <= 0) {
			*_len = dp - *_dp;
			*_dp = dp;
			return 0;
		}
		goto next_tag;
	}

	if (unlikely((tag & 0x1f) == ASN1_LONG_TAG)) {
		do {
			if (unlikely(datalen - dp < 2))
				goto data_overrun_error;
			tmp = data[dp++];
		} while (tmp & 0x80);
	}

	/* Extract the length */
	len = data[dp++];
	if (len <= 0x7f) {
		dp += len;
		goto next_tag;
	}

	if (unlikely(len == ASN1_INDEFINITE_LENGTH)) {
		/* Indefinite length */
		if (unlikely((tag & ASN1_CONS_BIT) == ASN1_PRIM << 5))
			goto indefinite_len_primitive;
		indef_level++;
		goto next_tag;
	}

	n = len - 0x80;
	if (unlikely(n > sizeof(size_t) - 1))
		goto length_too_long;
	if (unlikely(n > datalen - dp))
		goto data_overrun_error;
	for (len = 0; n > 0; n--) {
		len <<= 8;
		len |= data[dp++];
	}
	dp += len;
	goto next_tag;

length_too_long:
	*_errmsg = "Unsupported length";
	goto error;
indefinite_len_primitive:
	*_errmsg = "Indefinite len primitive not permitted";
	goto error;
invalid_eoc:
	*_errmsg = "Invalid length EOC";
	goto error;
data_overrun_error:
	*_errmsg = "Data overrun error";
	goto error;
missing_eoc:
	*_errmsg = "Missing EOC in indefinite len cons";
error:
	*_dp = dp;
	return -1;
}

/**
 * asn1_ber_decoder - Decoder BER/DER/CER ASN.1 according to pattern
 * @decoder: The decoder definition (produced by asn1_compiler)
 * @context: The caller's context (to be passed to the action functions)
 * @data: The encoded data
 * @datalen: The size of the encoded data
 *
 * Decode BER/DER/CER encoded ASN.1 data according to a bytecode pattern
 * produced by asn1_compiler.  Action functions are called on marked tags to
 * allow the caller to retrieve significant data.
 *
 * LIMITATIONS:
 *
 * To keep down the amount of stack used by this function, the following limits
 * have been imposed:
 *
 *  (1) This won't handle datalen > 65535 without increasing the size of the
 *	cons stack elements and length_too_long checking.
 *
 *  (2) The stack of constructed types is 10 deep.  If the depth of non-leaf
 *	constructed types exceeds this, the decode will fail.
 *
 *  (3) The SET type (not the SET OF type) isn't really supported as tracking
 *	what members of the set have been seen is a pain.
 */
int asn1_ber_decoder(const struct asn1_decoder *decoder,
		     void *context,
		     const unsigned char *data,
		     size_t datalen)
{
	const unsigned char *machine = decoder->machine;
	const asn1_action_t *actions = decoder->actions;
	size_t machlen = decoder->machlen;
	enum asn1_opcode op;
	unsigned char tag = 0, csp = 0, jsp = 0, optag = 0, hdr = 0;
	const char *errmsg;
	size_t pc = 0, dp = 0, tdp = 0, len = 0;
	int ret;

	unsigned char flags = 0;
#define FLAG_INDEFINITE_LENGTH	0x01
#define FLAG_MATCHED		0x02
#define FLAG_LAST_MATCHED	0x04 /* Last tag matched */
#define FLAG_CONS		0x20 /* Corresponds to CONS bit in the opcode tag
				      * - ie. whether or not we are going to parse
				      *   a compound type.
				      */

#define NR_CONS_STACK 10
	unsigned short cons_dp_stack[NR_CONS_STACK];
	unsigned short cons_datalen_stack[NR_CONS_STACK];
	unsigned char cons_hdrlen_stack[NR_CONS_STACK];
#define NR_JUMP_STACK 10
	unsigned char jump_stack[NR_JUMP_STACK];

	if (datalen > 65535)
		return -EMSGSIZE;

next_op:
	pr_debug("next_op: pc=\e[32m%zu\e[m/%zu dp=\e[33m%zu\e[m/%zu C=%d J=%d\n",
		 pc, machlen, dp, datalen, csp, jsp);
	if (unlikely(pc >= machlen))
		goto machine_overrun_error;
	op = machine[pc];
	if (unlikely(pc + asn1_op_lengths[op] > machlen))
		goto machine_overrun_error;

	/* If this command is meant to match a tag, then do that before
	 * evaluating the command.
	 */
	if (op <= ASN1_OP__MATCHES_TAG) {
		unsigned char tmp;

		/* Skip conditional matches if possible */
		if ((op & ASN1_OP_MATCH__COND && flags & FLAG_MATCHED) ||
		    (op & ASN1_OP_MATCH__SKIP && dp == datalen)) {
			flags &= ~FLAG_LAST_MATCHED;
			pc += asn1_op_lengths[op];
			goto next_op;
		}

		flags = 0;
		hdr = 2;

		/* Extract a tag from the data */
		if (unlikely(dp >= datalen - 1))
			goto data_overrun_error;
		tag = data[dp++];
		if (unlikely((tag & 0x1f) == ASN1_LONG_TAG))
			goto long_tag_not_supported;

		if (op & ASN1_OP_MATCH__ANY) {
			pr_debug("- any %02x\n", tag);
		} else {
			/* Extract the tag from the machine
			 * - Either CONS or PRIM are permitted in the data if
			 *   CONS is not set in the op stream, otherwise CONS
			 *   is mandatory.
			 */
			optag = machine[pc + 1];
			flags |= optag & FLAG_CONS;

			/* Determine whether the tag matched */
			tmp = optag ^ tag;
			tmp &= ~(optag & ASN1_CONS_BIT);
			pr_debug("- match? %02x %02x %02x\n", tag, optag, tmp);
			if (tmp != 0) {
				/* All odd-numbered tags are MATCH_OR_SKIP. */
				if (op & ASN1_OP_MATCH__SKIP) {
					pc += asn1_op_lengths[op];
					dp--;
					goto next_op;
				}
				goto tag_mismatch;
			}
		}
		flags |= FLAG_MATCHED;

		len = data[dp++];
		if (len > 0x7f) {
			if (unlikely(len == ASN1_INDEFINITE_LENGTH)) {
				/* Indefinite length */
				if (unlikely(!(tag & ASN1_CONS_BIT)))
					goto indefinite_len_primitive;
				flags |= FLAG_INDEFINITE_LENGTH;
				if (unlikely(2 > datalen - dp))
					goto data_overrun_error;
			} else {
				int n = len - 0x80;
				if (unlikely(n > 2))
					goto length_too_long;
				if (unlikely(dp >= datalen - n))
					goto data_overrun_error;
				hdr += n;
				for (len = 0; n > 0; n--) {
					len <<= 8;
					len |= data[dp++];
				}
				if (unlikely(len > datalen - dp))
					goto data_overrun_error;
			}
		}

		if (flags & FLAG_CONS) {
			/* For expected compound forms, we stack the positions
			 * of the start and end of the data.
			 */
			if (unlikely(csp >= NR_CONS_STACK))
				goto cons_stack_overflow;
			cons_dp_stack[csp] = dp;
			cons_hdrlen_stack[csp] = hdr;
			if (!(flags & FLAG_INDEFINITE_LENGTH)) {
				cons_datalen_stack[csp] = datalen;
				datalen = dp + len;
			} else {
				cons_datalen_stack[csp] = 0;
			}
			csp++;
		}

		pr_debug("- TAG: %02x %zu%s\n",
			 tag, len, flags & FLAG_CONS ? " CONS" : "");
		tdp = dp;
	}

	/* Decide how to handle the operation */
	switch (op) {
	case ASN1_OP_MATCH_ANY_ACT:
	case ASN1_OP_COND_MATCH_ANY_ACT:
		ret = actions[machine[pc + 1]](context, hdr, tag, data + dp, len);
		if (ret < 0)
			return ret;
		goto skip_data;

	case ASN1_OP_MATCH_ACT:
	case ASN1_OP_MATCH_ACT_OR_SKIP:
	case ASN1_OP_COND_MATCH_ACT_OR_SKIP:
		ret = actions[machine[pc + 2]](context, hdr, tag, data + dp, len);
		if (ret < 0)
			return ret;
		goto skip_data;

	case ASN1_OP_MATCH:
	case ASN1_OP_MATCH_OR_SKIP:
	case ASN1_OP_MATCH_ANY:
	case ASN1_OP_COND_MATCH_OR_SKIP:
	case ASN1_OP_COND_MATCH_ANY:
	skip_data:
		if (!(flags & FLAG_CONS)) {
			if (flags & FLAG_INDEFINITE_LENGTH) {
				ret = asn1_find_indefinite_length(
					data, datalen, &dp, &len, &errmsg);
				if (ret < 0)
					goto error;
			} else {
				dp += len;
			}
			pr_debug("- LEAF: %zu\n", len);
		}
		pc += asn1_op_lengths[op];
		goto next_op;

	case ASN1_OP_MATCH_JUMP:
	case ASN1_OP_MATCH_JUMP_OR_SKIP:
	case ASN1_OP_COND_MATCH_JUMP_OR_SKIP:
		pr_debug("- MATCH_JUMP\n");
		if (unlikely(jsp == NR_JUMP_STACK))
			goto jump_stack_overflow;
		jump_stack[jsp++] = pc + asn1_op_lengths[op];
		pc = machine[pc + 2];
		goto next_op;

	case ASN1_OP_COND_FAIL:
		if (unlikely(!(flags & FLAG_MATCHED)))
			goto tag_mismatch;
		pc += asn1_op_lengths[op];
		goto next_op;

	case ASN1_OP_COMPLETE:
		if (unlikely(jsp != 0 || csp != 0)) {
			pr_err("ASN.1 decoder error: Stacks not empty at completion (%u, %u)\n",
			       jsp, csp);
			return -EBADMSG;
		}
		return 0;

	case ASN1_OP_END_SET:
	case ASN1_OP_END_SET_ACT:
		if (unlikely(!(flags & FLAG_MATCHED)))
			goto tag_mismatch;
	case ASN1_OP_END_SEQ:
	case ASN1_OP_END_SET_OF:
	case ASN1_OP_END_SEQ_OF:
	case ASN1_OP_END_SEQ_ACT:
	case ASN1_OP_END_SET_OF_ACT:
	case ASN1_OP_END_SEQ_OF_ACT:
		if (unlikely(csp <= 0))
			goto cons_stack_underflow;
		csp--;
		tdp = cons_dp_stack[csp];
		hdr = cons_hdrlen_stack[csp];
		len = datalen;
		datalen = cons_datalen_stack[csp];
		pr_debug("- end cons t=%zu dp=%zu l=%zu/%zu\n",
			 tdp, dp, len, datalen);
		if (datalen == 0) {
			/* Indefinite length - check for the EOC. */
			datalen = len;
			if (unlikely(datalen - dp < 2))
				goto data_overrun_error;
			if (data[dp++] != 0) {
				if (op & ASN1_OP_END__OF) {
					dp--;
					csp++;
					pc = machine[pc + 1];
					pr_debug("- continue\n");
					goto next_op;
				}
				goto missing_eoc;
			}
			if (data[dp++] != 0)
				goto invalid_eoc;
			len = dp - tdp - 2;
		} else {
			if (dp < len && (op & ASN1_OP_END__OF)) {
				datalen = len;
				csp++;
				pc = machine[pc + 1];
				pr_debug("- continue\n");
				goto next_op;
			}
			if (dp != len)
				goto cons_length_error;
			len -= tdp;
			pr_debug("- cons len l=%zu d=%zu\n", len, dp - tdp);
		}

		if (op & ASN1_OP_END__ACT) {
			unsigned char act;
			if (op & ASN1_OP_END__OF)
				act = machine[pc + 2];
			else
				act = machine[pc + 1];
			ret = actions[act](context, hdr, 0, data + tdp, len);
		}
		pc += asn1_op_lengths[op];
		goto next_op;

	case ASN1_OP_MAYBE_ACT:
		if (!(flags & FLAG_LAST_MATCHED)) {
			pc += asn1_op_lengths[op];
			goto next_op;
		}
	case ASN1_OP_ACT:
		ret = actions[machine[pc + 1]](context, hdr, tag, data + tdp, len);
		if (ret < 0)
			return ret;
		pc += asn1_op_lengths[op];
		goto next_op;

	case ASN1_OP_RETURN:
		if (unlikely(jsp <= 0))
			goto jump_stack_underflow;
		pc = jump_stack[--jsp];
		flags |= FLAG_MATCHED | FLAG_LAST_MATCHED;
		goto next_op;

	default:
		break;
	}

	/* Shouldn't reach here */
	pr_err("ASN.1 decoder error: Found reserved opcode (%u) pc=%zu\n",
	       op, pc);
	return -EBADMSG;

data_overrun_error:
	errmsg = "Data overrun error";
	goto error;
machine_overrun_error:
	errmsg = "Machine overrun error";
	goto error;
jump_stack_underflow:
	errmsg = "Jump stack underflow";
	goto error;
jump_stack_overflow:
	errmsg = "Jump stack overflow";
	goto error;
cons_stack_underflow:
	errmsg = "Cons stack underflow";
	goto error;
cons_stack_overflow:
	errmsg = "Cons stack overflow";
	goto error;
cons_length_error:
	errmsg = "Cons length error";
	goto error;
missing_eoc:
	errmsg = "Missing EOC in indefinite len cons";
	goto error;
invalid_eoc:
	errmsg = "Invalid length EOC";
	goto error;
length_too_long:
	errmsg = "Unsupported length";
	goto error;
indefinite_len_primitive:
	errmsg = "Indefinite len primitive not permitted";
	goto error;
tag_mismatch:
	errmsg = "Unexpected tag";
	goto error;
long_tag_not_supported:
	errmsg = "Long tag not supported";
error:
	pr_debug("\nASN1: %s [m=%zu d=%zu ot=%02x t=%02x l=%zu]\n",
		 errmsg, pc, dp, optag, tag, len);
	return -EBADMSG;
}
EXPORT_SYMBOL_GPL(asn1_ber_decoder);
Commit	Line	Data
42d5ec27 DH	1	/* Decoder for ASN.1 BER/DER/CER encoded bytestream
	2	*
	3	* Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
	4	* Written by David Howells (dhowells@redhat.com)
	5	*
	6	* This program is free software; you can redistribute it and/or
	7	* modify it under the terms of the GNU General Public Licence
	8	* as published by the Free Software Foundation; either version
	9	* 2 of the Licence, or (at your option) any later version.
	10	*/
	11
	12	#include <linux/export.h>
	13	#include <linux/kernel.h>
	14	#include <linux/errno.h>
	15	#include <linux/asn1_decoder.h>
	16	#include <linux/asn1_ber_bytecode.h>
	17
	18	static const unsigned char asn1_op_lengths[ASN1_OP__NR] = {
	19	/* OPC TAG JMP ACT */
	20	[ASN1_OP_MATCH] = 1 + 1,
	21	[ASN1_OP_MATCH_OR_SKIP] = 1 + 1,
	22	[ASN1_OP_MATCH_ACT] = 1 + 1 + 1,
	23	[ASN1_OP_MATCH_ACT_OR_SKIP] = 1 + 1 + 1,
	24	[ASN1_OP_MATCH_JUMP] = 1 + 1 + 1,
	25	[ASN1_OP_MATCH_JUMP_OR_SKIP] = 1 + 1 + 1,
	26	[ASN1_OP_MATCH_ANY] = 1,
	27	[ASN1_OP_MATCH_ANY_ACT] = 1 + 1,
	28	[ASN1_OP_COND_MATCH_OR_SKIP] = 1 + 1,
	29	[ASN1_OP_COND_MATCH_ACT_OR_SKIP] = 1 + 1 + 1,
	30	[ASN1_OP_COND_MATCH_JUMP_OR_SKIP] = 1 + 1 + 1,
	31	[ASN1_OP_COND_MATCH_ANY] = 1,
	32	[ASN1_OP_COND_MATCH_ANY_ACT] = 1 + 1,
	33	[ASN1_OP_COND_FAIL] = 1,
	34	[ASN1_OP_COMPLETE] = 1,
	35	[ASN1_OP_ACT] = 1 + 1,
3f3af97d	36	[ASN1_OP_MAYBE_ACT] = 1 + 1,
42d5ec27 DH	37	[ASN1_OP_RETURN] = 1,
	38	[ASN1_OP_END_SEQ] = 1,
	39	[ASN1_OP_END_SEQ_OF] = 1 + 1,
	40	[ASN1_OP_END_SET] = 1,
	41	[ASN1_OP_END_SET_OF] = 1 + 1,
	42	[ASN1_OP_END_SEQ_ACT] = 1 + 1,
	43	[ASN1_OP_END_SEQ_OF_ACT] = 1 + 1 + 1,
	44	[ASN1_OP_END_SET_ACT] = 1 + 1,
	45	[ASN1_OP_END_SET_OF_ACT] = 1 + 1 + 1,
	46	};
	47
	48	/*
	49	* Find the length of an indefinite length object
dbadc176 DH	50	* @data: The data buffer
	51	* @datalen: The end of the innermost containing element in the buffer
	52	* @_dp: The data parse cursor (updated before returning)
	53	* @_len: Where to return the size of the element.
	54	* @_errmsg: Where to return a pointer to an error message on error
42d5ec27 DH	55	*/
42d5ec27 DH	56	static int asn1_find_indefinite_length(const unsigned char *data, size_t datalen,
dbadc176 DH	57	size_t _dp, size_t _len,
dbadc176 DH	58	const char **_errmsg)
42d5ec27 DH	59	{
42d5ec27 DH	60	unsigned char tag, tmp;
dbadc176	61	size_t dp = *_dp, len, n;
42d5ec27 DH	62	int indef_level = 1;
	63
	64	next_tag:
	65	if (unlikely(datalen - dp < 2)) {
	66	if (datalen == dp)
	67	goto missing_eoc;
	68	goto data_overrun_error;
	69	}
	70
	71	/* Extract a tag from the data */
	72	tag = data[dp++];
	73	if (tag == 0) {
	74	/* It appears to be an EOC. */
	75	if (data[dp++] != 0)
	76	goto invalid_eoc;
dbadc176 DH	77	if (--indef_level <= 0) {
	78	_len = dp - _dp;
	79	*_dp = dp;
	80	return 0;
	81	}
42d5ec27 DH	82	goto next_tag;
	83	}
	84
99cca91e	85	if (unlikely((tag & 0x1f) == ASN1_LONG_TAG)) {
42d5ec27 DH	86	do {
	87	if (unlikely(datalen - dp < 2))
	88	goto data_overrun_error;
	89	tmp = data[dp++];
	90	} while (tmp & 0x80);
	91	}
	92
	93	/* Extract the length */
	94	len = data[dp++];
f3537f91	95	if (len <= 0x7f) {
42d5ec27 DH	96	dp += len;
	97	goto next_tag;
	98	}
	99
99cca91e	100	if (unlikely(len == ASN1_INDEFINITE_LENGTH)) {
42d5ec27 DH	101	/* Indefinite length */
	102	if (unlikely((tag & ASN1_CONS_BIT) == ASN1_PRIM << 5))
	103	goto indefinite_len_primitive;
	104	indef_level++;
	105	goto next_tag;
	106	}
	107
	108	n = len - 0x80;
	109	if (unlikely(n > sizeof(size_t) - 1))
	110	goto length_too_long;
	111	if (unlikely(n > datalen - dp))
	112	goto data_overrun_error;
	113	for (len = 0; n > 0; n--) {
	114	len <<= 8;
	115	len \|= data[dp++];
	116	}
	117	dp += len;
	118	goto next_tag;
	119
	120	length_too_long:
	121	*_errmsg = "Unsupported length";
	122	goto error;
	123	indefinite_len_primitive:
	124	*_errmsg = "Indefinite len primitive not permitted";
	125	goto error;
	126	invalid_eoc:
	127	*_errmsg = "Invalid length EOC";
	128	goto error;
	129	data_overrun_error:
	130	*_errmsg = "Data overrun error";
	131	goto error;
	132	missing_eoc:
	133	*_errmsg = "Missing EOC in indefinite len cons";
	134	error:
dbadc176	135	*_dp = dp;
42d5ec27 DH	136	return -1;
	137	}
	138
	139	/**
	140	* asn1_ber_decoder - Decoder BER/DER/CER ASN.1 according to pattern
	141	* @decoder: The decoder definition (produced by asn1_compiler)
	142	* @context: The caller's context (to be passed to the action functions)
	143	* @data: The encoded data
548bbff9	144	* @datalen: The size of the encoded data
42d5ec27 DH	145	*
	146	* Decode BER/DER/CER encoded ASN.1 data according to a bytecode pattern
	147	* produced by asn1_compiler. Action functions are called on marked tags to
	148	* allow the caller to retrieve significant data.
	149	*
	150	* LIMITATIONS:
	151	*
	152	* To keep down the amount of stack used by this function, the following limits
	153	* have been imposed:
	154	*
	155	* (1) This won't handle datalen > 65535 without increasing the size of the
	156	* cons stack elements and length_too_long checking.
	157	*
	158	* (2) The stack of constructed types is 10 deep. If the depth of non-leaf
	159	* constructed types exceeds this, the decode will fail.
	160	*
	161	* (3) The SET type (not the SET OF type) isn't really supported as tracking
	162	* what members of the set have been seen is a pain.
	163	*/
	164	int asn1_ber_decoder(const struct asn1_decoder *decoder,
	165	void *context,
	166	const unsigned char *data,
	167	size_t datalen)
	168	{
	169	const unsigned char *machine = decoder->machine;
	170	const asn1_action_t *actions = decoder->actions;
	171	size_t machlen = decoder->machlen;
	172	enum asn1_opcode op;
	173	unsigned char tag = 0, csp = 0, jsp = 0, optag = 0, hdr = 0;
	174	const char *errmsg;
	175	size_t pc = 0, dp = 0, tdp = 0, len = 0;
	176	int ret;
	177
	178	unsigned char flags = 0;
	179	#define FLAG_INDEFINITE_LENGTH 0x01
	180	#define FLAG_MATCHED 0x02
3f3af97d	181	#define FLAG_LAST_MATCHED 0x04 /* Last tag matched */
42d5ec27 DH	182	#define FLAG_CONS 0x20 /* Corresponds to CONS bit in the opcode tag
	183	* - ie. whether or not we are going to parse
	184	* a compound type.
	185	*/
	186
	187	#define NR_CONS_STACK 10
	188	unsigned short cons_dp_stack[NR_CONS_STACK];
	189	unsigned short cons_datalen_stack[NR_CONS_STACK];
	190	unsigned char cons_hdrlen_stack[NR_CONS_STACK];
	191	#define NR_JUMP_STACK 10
	192	unsigned char jump_stack[NR_JUMP_STACK];
	193
	194	if (datalen > 65535)
	195	return -EMSGSIZE;
	196
	197	next_op:
	198	pr_debug("next_op: pc=\e[32m%zu\e[m/%zu dp=\e[33m%zu\e[m/%zu C=%d J=%d\n",
	199	pc, machlen, dp, datalen, csp, jsp);
	200	if (unlikely(pc >= machlen))
	201	goto machine_overrun_error;
	202	op = machine[pc];
	203	if (unlikely(pc + asn1_op_lengths[op] > machlen))
	204	goto machine_overrun_error;
	205
	206	/* If this command is meant to match a tag, then do that before
	207	* evaluating the command.
	208	*/
	209	if (op <= ASN1_OP__MATCHES_TAG) {
	210	unsigned char tmp;
	211
	212	/* Skip conditional matches if possible */
0d62e9dd DH	213	if ((op & ASN1_OP_MATCH__COND && flags & FLAG_MATCHED) \|\|
0d62e9dd DH	214	(op & ASN1_OP_MATCH__SKIP && dp == datalen)) {
3f3af97d	215	flags &= ~FLAG_LAST_MATCHED;
42d5ec27 DH	216	pc += asn1_op_lengths[op];
	217	goto next_op;
	218	}
	219
	220	flags = 0;
	221	hdr = 2;
	222
	223	/* Extract a tag from the data */
	224	if (unlikely(dp >= datalen - 1))
	225	goto data_overrun_error;
	226	tag = data[dp++];
99cca91e	227	if (unlikely((tag & 0x1f) == ASN1_LONG_TAG))
42d5ec27 DH	228	goto long_tag_not_supported;
	229
	230	if (op & ASN1_OP_MATCH__ANY) {
	231	pr_debug("- any %02x\n", tag);
	232	} else {
	233	/* Extract the tag from the machine
	234	* - Either CONS or PRIM are permitted in the data if
	235	* CONS is not set in the op stream, otherwise CONS
	236	* is mandatory.
	237	*/
	238	optag = machine[pc + 1];
	239	flags \|= optag & FLAG_CONS;
	240
	241	/* Determine whether the tag matched */
	242	tmp = optag ^ tag;
	243	tmp &= ~(optag & ASN1_CONS_BIT);
	244	pr_debug("- match? %02x %02x %02x\n", tag, optag, tmp);
	245	if (tmp != 0) {
	246	/* All odd-numbered tags are MATCH_OR_SKIP. */
	247	if (op & ASN1_OP_MATCH__SKIP) {
	248	pc += asn1_op_lengths[op];
	249	dp--;
	250	goto next_op;
	251	}
	252	goto tag_mismatch;
	253	}
	254	}
	255	flags \|= FLAG_MATCHED;
	256
	257	len = data[dp++];
	258	if (len > 0x7f) {
99cca91e	259	if (unlikely(len == ASN1_INDEFINITE_LENGTH)) {
42d5ec27 DH	260	/* Indefinite length */
	261	if (unlikely(!(tag & ASN1_CONS_BIT)))
	262	goto indefinite_len_primitive;
	263	flags \|= FLAG_INDEFINITE_LENGTH;
	264	if (unlikely(2 > datalen - dp))
	265	goto data_overrun_error;
	266	} else {
	267	int n = len - 0x80;
	268	if (unlikely(n > 2))
	269	goto length_too_long;
	270	if (unlikely(dp >= datalen - n))
	271	goto data_overrun_error;
	272	hdr += n;
	273	for (len = 0; n > 0; n--) {
	274	len <<= 8;
	275	len \|= data[dp++];
	276	}
	277	if (unlikely(len > datalen - dp))
	278	goto data_overrun_error;
	279	}
	280	}
	281
	282	if (flags & FLAG_CONS) {
	283	/* For expected compound forms, we stack the positions
	284	* of the start and end of the data.
	285	*/
	286	if (unlikely(csp >= NR_CONS_STACK))
	287	goto cons_stack_overflow;
	288	cons_dp_stack[csp] = dp;
	289	cons_hdrlen_stack[csp] = hdr;
	290	if (!(flags & FLAG_INDEFINITE_LENGTH)) {
	291	cons_datalen_stack[csp] = datalen;
	292	datalen = dp + len;
	293	} else {
	294	cons_datalen_stack[csp] = 0;
	295	}
	296	csp++;
	297	}
	298
	299	pr_debug("- TAG: %02x %zu%s\n",
	300	tag, len, flags & FLAG_CONS ? " CONS" : "");
	301	tdp = dp;
	302	}
	303
	304	/* Decide how to handle the operation */
	305	switch (op) {
	306	case ASN1_OP_MATCH_ANY_ACT:
	307	case ASN1_OP_COND_MATCH_ANY_ACT:
	308	ret = actions[machine[pc + 1]](context, hdr, tag, data + dp, len);
	309	if (ret < 0)
	310	return ret;
	311	goto skip_data;
	312
	313	case ASN1_OP_MATCH_ACT:
	314	case ASN1_OP_MATCH_ACT_OR_SKIP:
	315	case ASN1_OP_COND_MATCH_ACT_OR_SKIP:
	316	ret = actions[machine[pc + 2]](context, hdr, tag, data + dp, len);
	317	if (ret < 0)
	318	return ret;
	319	goto skip_data;
	320
	321	case ASN1_OP_MATCH:
	322	case ASN1_OP_MATCH_OR_SKIP:
	323	case ASN1_OP_MATCH_ANY:
324	case ASN1_OP_COND_MATCH_OR_SKIP:
325	case ASN1_OP_COND_MATCH_ANY:
326	skip_data:
327	if (!(flags & FLAG_CONS)) {
328	if (flags & FLAG_INDEFINITE_LENGTH) {
dbadc176 DH	329	ret = asn1_find_indefinite_length(
	330	data, datalen, &dp, &len, &errmsg);
	331	if (ret < 0)
42d5ec27	332	goto error;
dbadc176 DH	333	} else {
dbadc176 DH	334	dp += len;
42d5ec27 DH	335	}
42d5ec27 DH	336	pr_debug("- LEAF: %zu\n", len);
42d5ec27 DH	337	}
	338	pc += asn1_op_lengths[op];
	339	goto next_op;
	340
	341	case ASN1_OP_MATCH_JUMP:
	342	case ASN1_OP_MATCH_JUMP_OR_SKIP:
	343	case ASN1_OP_COND_MATCH_JUMP_OR_SKIP:
	344	pr_debug("- MATCH_JUMP\n");
	345	if (unlikely(jsp == NR_JUMP_STACK))
	346	goto jump_stack_overflow;
	347	jump_stack[jsp++] = pc + asn1_op_lengths[op];
	348	pc = machine[pc + 2];
	349	goto next_op;
	350
	351	case ASN1_OP_COND_FAIL:
	352	if (unlikely(!(flags & FLAG_MATCHED)))
	353	goto tag_mismatch;
	354	pc += asn1_op_lengths[op];
	355	goto next_op;
	356
	357	case ASN1_OP_COMPLETE:
	358	if (unlikely(jsp != 0 \|\| csp != 0)) {
	359	pr_err("ASN.1 decoder error: Stacks not empty at completion (%u, %u)\n",
	360	jsp, csp);
	361	return -EBADMSG;
	362	}
	363	return 0;
	364
	365	case ASN1_OP_END_SET:
	366	case ASN1_OP_END_SET_ACT:
	367	if (unlikely(!(flags & FLAG_MATCHED)))
	368	goto tag_mismatch;
	369	case ASN1_OP_END_SEQ:
	370	case ASN1_OP_END_SET_OF:
	371	case ASN1_OP_END_SEQ_OF:
	372	case ASN1_OP_END_SEQ_ACT:
	373	case ASN1_OP_END_SET_OF_ACT:
	374	case ASN1_OP_END_SEQ_OF_ACT:
	375	if (unlikely(csp <= 0))
	376	goto cons_stack_underflow;
	377	csp--;
	378	tdp = cons_dp_stack[csp];
	379	hdr = cons_hdrlen_stack[csp];
	380	len = datalen;
	381	datalen = cons_datalen_stack[csp];
	382	pr_debug("- end cons t=%zu dp=%zu l=%zu/%zu\n",
	383	tdp, dp, len, datalen);
	384	if (datalen == 0) {
	385	/* Indefinite length - check for the EOC. */
	386	datalen = len;
	387	if (unlikely(datalen - dp < 2))
	388	goto data_overrun_error;
	389	if (data[dp++] != 0) {
	390	if (op & ASN1_OP_END__OF) {
	391	dp--;
	392	csp++;
	393	pc = machine[pc + 1];
	394	pr_debug("- continue\n");
	395	goto next_op;
	396	}
	397	goto missing_eoc;
	398	}
	399	if (data[dp++] != 0)
	400	goto invalid_eoc;
401	len = dp - tdp - 2;
402	} else {
403	if (dp < len && (op & ASN1_OP_END__OF)) {
404	datalen = len;
405	csp++;
406	pc = machine[pc + 1];
407	pr_debug("- continue\n");
408	goto next_op;
409	}
410	if (dp != len)
411	goto cons_length_error;
412	len -= tdp;
413	pr_debug("- cons len l=%zu d=%zu\n", len, dp - tdp);
414	}
415
416	if (op & ASN1_OP_END__ACT) {
417	unsigned char act;
418	if (op & ASN1_OP_END__OF)
419	act = machine[pc + 2];
420	else
421	act = machine[pc + 1];
422	ret = actions[act](context, hdr, 0, data + tdp, len);
423	}
424	pc += asn1_op_lengths[op];
425	goto next_op;
426
3f3af97d DH	427	case ASN1_OP_MAYBE_ACT:
	428	if (!(flags & FLAG_LAST_MATCHED)) {
	429	pc += asn1_op_lengths[op];
	430	goto next_op;
	431	}
42d5ec27 DH	432	case ASN1_OP_ACT:
42d5ec27 DH	433	ret = actions[machine[pc + 1]](context, hdr, tag, data + tdp, len);
3f3af97d DH	434	if (ret < 0)
3f3af97d DH	435	return ret;
42d5ec27 DH	436	pc += asn1_op_lengths[op];
	437	goto next_op;
	438
	439	case ASN1_OP_RETURN:
	440	if (unlikely(jsp <= 0))
	441	goto jump_stack_underflow;
	442	pc = jump_stack[--jsp];
3f3af97d	443	flags \|= FLAG_MATCHED \| FLAG_LAST_MATCHED;
42d5ec27 DH	444	goto next_op;
	445
	446	default:
	447	break;
	448	}
	449
	450	/* Shouldn't reach here */
3f3af97d DH	451	pr_err("ASN.1 decoder error: Found reserved opcode (%u) pc=%zu\n",
3f3af97d DH	452	op, pc);
42d5ec27 DH	453	return -EBADMSG;
	454
	455	data_overrun_error:
	456	errmsg = "Data overrun error";
	457	goto error;
	458	machine_overrun_error:
	459	errmsg = "Machine overrun error";
	460	goto error;
	461	jump_stack_underflow:
	462	errmsg = "Jump stack underflow";
	463	goto error;
	464	jump_stack_overflow:
	465	errmsg = "Jump stack overflow";
	466	goto error;
	467	cons_stack_underflow:
	468	errmsg = "Cons stack underflow";
	469	goto error;
	470	cons_stack_overflow:
	471	errmsg = "Cons stack overflow";
	472	goto error;
	473	cons_length_error:
	474	errmsg = "Cons length error";
	475	goto error;
	476	missing_eoc:
	477	errmsg = "Missing EOC in indefinite len cons";
	478	goto error;
	479	invalid_eoc:
	480	errmsg = "Invalid length EOC";
	481	goto error;
	482	length_too_long:
	483	errmsg = "Unsupported length";
	484	goto error;
	485	indefinite_len_primitive:
	486	errmsg = "Indefinite len primitive not permitted";
	487	goto error;
	488	tag_mismatch:
	489	errmsg = "Unexpected tag";
	490	goto error;
	491	long_tag_not_supported:
	492	errmsg = "Long tag not supported";
	493	error:
	494	pr_debug("\nASN1: %s [m=%zu d=%zu ot=%02x t=%02x l=%zu]\n",
	495	errmsg, pc, dp, optag, tag, len);
	496	return -EBADMSG;
	497	}
	498	EXPORT_SYMBOL_GPL(asn1_ber_decoder);